traceroute does not respond with -F fragment option

[guruvenkatesh]

Hi I am newbie to linux networking side, can someone help to resolve the following

traceroute -r -F ldvdora02 46
traceroute to ldvdora02.erplance.com (172.16.2.106), 30 hops max, 46 byte packets
1 * * *
2 * * *
3 * * *
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
9 * * *
10 * * *
11 * * *
12 * * *
13 * * *
14 * * *
15 * * *
16 * * *
17 * * *
18 * * *
19 * * *

When we do it without -F option it works fine

traceroute ldvdora02
traceroute to ldvdora02.erplance.com (172.16.2.106), 30 hops max, 46 byte packets
1 ldvdora02 (172.16.2.106) 0.138 ms 0.119 ms 0.102 ms

[scathefire]

most routers, firewall, etc. are setup to drop fragments, as they are a typically used to circumvent security devices. fragmentation is way old and protocols have matured to the point where fragmentation is not necessary, therefore it is blocked by basically everyone. you have to force most routers to accept fragmented packets now a days

[guruvenkatesh]

Thanks for your quick response.

traceroute to local host is also failing if i give the -F parameter. Does traceroute go thru the firewall configuration even for the localhost?

[root@ldvdora01 ~]# traceroute -r localhost

traceroute to localhost.localdomain (127.0.0.1), 30 hops max, 46 byte packets

1 localhost.localdomain (127.0.0.1) 0.041 ms 0.021 ms 0.018 ms

[root@ldvdora01 ~]# traceroute -r -F localhost 46

traceroute to localhost.localdomain (127.0.0.1), 30 hops max, 46 byte packets
1 * * *
2 * * *

Why my localhost doesn't respond to traceroute with –F option?

Is there any interface problem?

[scathefire]

according to all the man pages i've been reading -F is DON'T fragment (oops ). By default, linux uses UDP for traceroutes, unlike windows which uses ICMP (that is just fyi if you didn't know). Maybe it doesn't like that flag in the packets.

[Lazydog]

[root@ldvdora01 ~]# traceroute -r -F localhost 46

Here is something to think about. Your packet size is not big enough to be fragmented. 46 bytes is nothing so why do you even think you need the '-F' flag?

[guruvenkatesh]

We tried even with larger size it doesnt work. We have couple of other servers that handle our voip those servers run Linux too, they dont have this problem. We are not sure on which configuration files to check to find the difference in the setup.

[guruvenkatesh]

On RHEL3, RHEL4 do not use the '-F' argument for traceroute. If it is crucial to have the functionality, only for 2.6 kernels (RHEL4 and OEL4) it is still possible to download the latest source tarball from sourceforge.net/projects/traceroute Traceroute for Linux (2.0.12 as of November 27, 200 and build it on the distribution.